fyi: as i couldn't find a windows port of the xa/dxa package, I've first tried that under freebsd (worked great!) - now I've created a win32 port:

https://github.com/Dennis1000/xa65-win32

sorry, I was so frustated because a trivial task wasted that much time.

Just tried dxa/xa on freebsd:
dxa65 -g a000 basic.901226-01.bin >basic.src
and
xa65 basic.src
puts the starting address ($a000) at the first 2 bytes, can't find how to omit them ;-)

after running a
dd bs=2 skip=1 if=a ...

The binary will probably include data too, and that won't disassemble into instructions.
I don't care about those data - if the disassembler can't produce code it should just print a "db 0x55" or whatever (that's one problem: some print "db", sometimes with "," sometimes only spaces allowed, some ...

after trying endless hours different asm/dasmx/cc, I finally give up and ask you for help:
I have a 6502 binary (for testing purposes I'm using the cbm basic v2.bin, since its disassembly is very well documented) and want to run a disassembler
which output is then fed into an assembler and it should ...

thank you both for your suggestions. Using Bruce Clarks test ($12-$21=$91 SBC decimal) I've managed to find a small typo. Now the test completes! I still recommend providing a complete trace log of the test suite, it surely helps to find those bugs far easier! Thanks Klaus again for your effort ...

Thanks Klaus for your testing suite. I'm currently stuck on my 6502 emulator, and can't find out what's wrong. It runs till test 42 ($3249) and halts on ($335A), using the the functional test bin found in the NESkell https://github.com/blitzcode/neskell/tree/master/src/tests/6502_functional_tests ...